Portable image display

ABSTRACT

The object of the invention is to make a viewing unit of the image display compact so that it can be mounted on portable telephones or information terminals. The portable image display of the invention comprises a speaker portion, a microphone portion, an image display device  9  and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power. The viewing optical system is constructed of at least one prism member  10  comprising an entrance surface through which a light beam emanating from the image display device  9  is entered into the prism, at least one reflecting surface at which the light beam is reflected within the prism and an exit surface through which the light beam leaves the prism. The at least one reflecting surface has a curved surface shape for imparting power to a light beam. The curved surface shape is defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.

This application claims benefit of Japanese Application No. 2000-151462filed in Japan On May 23, 2000, the contents of which are incorporatedby this reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to a portable image display, andmore particularly to a portable image display that can be added toportable telephones or portable information terminals.

In recent years, image displays, especially head or face mounted imagedisplays designed to allow individuals to enjoy images on large screensor for other purposes have been under intensive developments. With therecent spread of portable telephones or information terminals, there isalso a growing demand for viewing images or textual information onportable telephones or information terminals on large screens.

Among head mounted image displays known so far in the art, there is adisplay system comprising a CRT or other image display device, an imagetransmission device for transmitting an image on the image displaydevice to an object plane and a toric reflecting surface for projectingthe image on the object plane in the air (see U.S. Pat. No. 4,026,641).There is also available a refraction type image display systemcomprising a relay optical device for forming an image on a liquidcrystal display (LCD) or other image display device in the air, and aneyepiece optical device including a decentered concave mirror forguiding the thus formed image to the eyeball of an observer (see JP-A06-294943).

However, these systems, because of using a large optical system, arefound to be unsuitable for use on portable telephones or informationterminals.

SUMMARY OF THE INVENTION

In view of such problems with prior art as mentioned above, an object ofthe present invention is to make an observation portion of an imagedisplay system so compact that it can be mounted on a portable telephoneor information terminal.

According to one aspect of the present invention, this object isachieved by the provision of a portable image display having datacommunication means, which comprises a speaker portion for catchingsounds, a microphone portion for picking up sounds, an image displaydevice and a viewing optical system for forming an exit pupil to view animage displayed on the image display device and having a generallypositive refracting power, characterized in that:

said viewing optical system is constructed of at least one prism membercomprising an entrance surface through which a light beam emanating fromsaid image display device is entered into a prism, at least onereflecting surface at which said light beam is reflected within theprism and an exit surface through which said light beam leaves theprism, wherein said at least one reflecting surface has a curved surfaceshape for imparting power to a light beam, said curved surface shapebeing defined by a rotationally asymmetric surface shape capable ofmaking correction for decentration aberrations.

Reference is now made to the action of this arrangement. Especially fora portable image display increasingly required to have smaller size, itis preferable that the optical system for forming an exit pupil andhaving a positive refracting power is constructed of one prism memberhaving a lens action. By use of one prism member, it is possible toachieve an optical system of smaller size. To obtain satisfactoryaberration performance, it is preferable that the prism member comprisesan entrance surface through which a light beam emanating from an imagedisplay device is entered into a prism, at least one reflecting surfaceat which the light beam is reflected within the prism and an exitsurface through which the light beam leaves the prism, wherein said atleast one reflecting surface has a curved surface shape for impartingpower to a light beam, said curved surface shape being defined by arotationally asymmetric surface shape capable of making correction fordecentration aberrations.

According to the second aspect of the present invention, there isprovided a portable image display having data communication means, whichcomprises an image display device and a viewing optical system forforming an exit pupil to view an image displayed on the image displaydevice and having a generally positive refracting power, characterizedin that:

said viewing optical system comprises a prism portion and a reflectingportion having a reflecting surface,

said image display device and said prism portion are received in a bodyof said portable image display,

said reflecting portion is held by a separate frame member, and

said frame member is receivable in said body.

Reference is now made to the action of this arrangement. To achieve anoptical system of smaller size for a portable image display, it iseffective to make use of a reflecting portion held by a frame memberreceivable in the body thereof. As mentioned above, size reductions maybe accomplished by use of one prism member. If the reflecting memberhaving a reflecting surface is designed to be receivable in the body,then the size of the portable image display can be much more reduced.

According to the third aspect of the present invention, there isprovided a portable image display having data communication means, whichcomprises a speaker portion for catching sounds, a microphone portionfor picking up sounds, an image display device, a viewing optical systemfor forming an exit pupil to view an image displayed on the imagedisplay device and having a generally positive refracting power, animage pickup device and an image pickup optical system for forming animage on the image pickup device, characterized in that:

said viewing optical system is constructed of at least one prism member.

Reference is now made to the action of this arrangement. The portableimage display of the present invention may further comprise an imagepickup device and an image pickup optical system for forming an image onthe image pickup device. To reduce the entire size of the image display,it is preferable that the viewing optical system is constructed of atleast one prism member.

According to the fourth aspect of the present invention, there isprovided a portable image display having data communication means,characterized by comprising a first image display device having a pixelpitch Pm, a second image display device having a pixel pitch Pn and aviewing optical system for forming an exit pupil to view an imagedisplayed on the first image display device and having a generallypositive refracting power, and satisfying the following condition (1):

0.01<Pm/Pn<0.8  (1)

The action of this arrangement is now explained. With a portable imagedisplay, textual or imagewise data on a display device are directlyviewed or viewed on an enlarged scale. Especially when images of highdefinition are viewed through a viewing optical system having agenerally positive refracting power on an enlarged scale, it ispreferable to make use of an image display device having a fine pixelpitch. For direct viewing of images not through any magnifying opticalsystem, on the other hand, no problem arises even when the pixel pitchis more or less large. Usually, an image display device having a finepixel pitch is unfavorable in terms of cost. Accordingly, it ispreferable to make use of an image display device having a large pixelpitch for direct-view purposes. For these reasons, the present inventionuses a direct-view display device and a magnifying display device whichsatisfy condition (1).

To improve the easy-to-carry capability of the portable image display,it is required to make the magnifying optical system compact. For directviewing with ease of use, on the other hand, this optical system musthave a large display area. To this end the following condition (2)should preferably be satisfied.

0.01<Sm/Sn<0.5  (2)

Here Sm is the display area of the magnifying image display device andSn is the display area of the direct-view image display device.

To allow the portable image display of the present invention to achievehigh-definition views of a magnified image with size and costreductions, it is preferable to satisfy both conditions (1) and (2).

According to the fifth aspect of the present invention, there isprovided a portable image display having data communication means,characterized by comprising a data storage means, a means for indicatingthe end of data reception, an image display device and a viewing opticalsystem for forming an exit pupil to view an image displayed on the imagedisplay device and having a generally positive refracting power.

Reference is now made to the action of this arrangement. When an imageis viewed through the viewing optical system, the user does not oftenpeer through the viewing optical system during reception of the data tobe viewed. Especially when the data are viewed on an enlarged scale, along-duration view offers user fatigue. For this reason, it ispreferable to provide the means for indicating the end of datareception. For instance, the end of data reception may be indicated byallowing a light to come on or a sound.

In the present invention, it is preferable to satisfy condition (1).More preferably, however, the following condition (1-2) should besatisfied.

0.03<Pm/Pn<0.5  (1-2)

In the present invention, it is preferable to satisfy condition (2).More preferably, however, the following condition (2-2) should besatisfied.

0.04<Sm/Sn<0.3  (2-2)

For correction of aberrations, the prism member used for the viewingoptical system should preferably comprise at least two surfaces forreflecting a light beam within a prism. Preferably in this case, said atleast two surfaces are each defined by a rotationally asymmetric surfaceshape.

In each of the arrangements according to the present invention, it ispreferable to use a data storage means for magnified viewing.

For instance, images transmitted using a communication function aredisplayed on the image display device, so that they are viewed on anenlarged scale through the viewing optical system. To retrieve therequired data or transmit them to separate equipment, it is preferableto provide storage means for storing the desired data.

In each of the arrangements of the present invention, there shouldpreferably be provided a light source for illuminating the image displaydevice and an illumination optical system for illuminating the imagedisplay device.

In each of the arrangements of the present invention, it is preferablefor energy savings that when a plurality of image display devices areused, the image display devices not in service are not illuminated.

In each of the arrangements of the present invention, it is preferablethat when an image on the image display device is viewed, the image isturned on the basis of whether the body of the portable image display isheld by the right hand or the left hand.

In each of the arrangements of the present invention, it is preferablethat the microphone portion for picking up sounds extends from the bodyof the portable image display such as a portable telephone.

In each of the arrangements of the present invention, it is preferablethat the speaker portion for catching sounds extends from the body ofthe portable image display such as a portable telephone.

In each of the arrangements of the present invention, it is preferablethat the speaker portion, operating portion and magnifying viewingoptical system are mounted in order from the top side of the body.

In each of the arrangements of the present invention, it is preferablethat a liquid crystal display (LCD) or plasma display may be used forthe image display device.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the construction of the portable imagedisplay according to Example 1 of the invention.

FIG. 2 is a side view illustrative of the construction and action of aviewing unit in Example 1.

FIG. 3 is an optical path diagram for a viewing optical system used inExample 1.

FIG. 4 is a pictorial view illustrative of how to use the portable imagedisplay according to Example 1.

FIG. 5 is illustrative of one example of an illumination optical systemfor the viewing unit in Example 1.

FIG. 6 is a perspective view of the construction of the portable imagedisplay according to Example 2 of the invention.

FIG. 7 is a side view illustrative of the construction and action of aviewing unit in Example 2.

FIG. 8 is an optical path diagram for a viewing optical system used inExample 2.

FIG. 9 is a perspective view illustrative of the construction of theportable image display according to Example 3 of the invention.

FIG. 10 is a perspective view illustrative of the construction ofanother embodiment of the portable image display according to Example 3of the invention.

FIG. 11 is a perspective view illustrative of the construction of theportable image display according to Example 4 of the invention.

FIG. 12 is a perspective view illustrative of the construction of theportable image display according to Example 5 of the invention.

FIG. 13 is an optical path diagram for another embodiment of the opticalsystem usable for the viewing optical system according to Example 1.

FIG. 14 is an optical path diagram for yet another embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 15 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 16 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 17 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 18 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 19 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 20 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 1.

FIG. 21 is an optical path diagram for another embodiment of the opticalsystem usable for the viewing optical system according to Example 2.

FIG. 22 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 2.

FIG. 23 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 2.

FIG. 24 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 2.

FIG. 25 is an optical path diagram for a further embodiment of theoptical system usable for the viewing optical system according toExample 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The portable image display of the present invention is now explainedwith reference to some preferred examples.

EXAMPLE 1

Example 1 is constructed as shown in the perspective view of FIG. 1,wherein 1 indicates a portable image display body, 2 a viewing unit, 3 aspeaker portion, 4 a microphone portion, 5 an antenna portion, 6 adirect-view liquid crystal display unit, 7 a set of push buttons, 8 anoperating stick portion, and 21 a signal light for indicating the end ofdata reception. It is here noted that the end of data reception may alsobe indicated by sounds.

As shown in FIG. 2, the viewing unit 2 comprises an LCD or other imagedisplay device 9 and a prism member 10 for viewing an image displayed onthe image display device. The viewing unit 2 is mechanically connectedto the body 1 at a lower site 20 of the body 1 while, when not used asshown by a dotted line 11 in FIG. 2, the viewing unit 2 can be foldeddown on the body 1, so that a compact portable image display can beachieved.

The viewing unit 2 constructed in such a way that it can be folded downon the body 1 does not only achieve compactness but also ensures thatwhen the viewing unit 2 is not in service, any possible damage to theprism member 10 can be prevented. This is because when the viewing unit2 is folded down, the exit surface 14 (FIG. 3) of the prism member 10 ispositioned in proximity to the body 1 and so is concealed from theoutside.

The prism member 10 used in the viewing optical system comprises, asshown in FIG. 3, an entrance surface 12 for entering a light beamemerging from the image display device 9 into the prism, at least onereflecting surface 13 for reflecting the light beam in the prism, and anexit surface 14 from which the light beam emerges. The reflectingsurface has a curved surface shape for imparting power to the lightbeam. Preferably in this example, the curved surface shape should bedefined by a rotationally asymmetric surface shape capable of makingsatisfactory correction for various decentration aberrations of theprism and making the prism compact. The light beam leaving the imagedisplay device 9 is totally reflected at the combined exit andreflecting surface 14 upon transmission through the entrance surface 12,and then reflected at the reflecting surface 13 with an antireflectioncoating thereon. Finally, the light beam leaves the exit surface in theform of a substantially infinite light beam.

In this example, the viewing unit 2 comprises a magnifying displaydevice 9 and the direct-view display device 6 having such specificationsas set out below.

TABLE 1 Pixel Pitch μm Size (H × V) mm Display Device 9 0.012 9.6 × 7.2Display Device 6 0.25 30 × 40

Instead of the magnifying display device 9 shown in Table 1, anothermagnifying display device of 0.038 μm or 0.005 μm in pixel pitch may beused for the portable image display of the invention.

Instead of the direct-view display device 6 shown in Table 1, anotherdirect-view display device of 0.12 μm or 0.058 μm in pixel pitch may beused for the portable image display of the invention.

Instead of the magnifying display device 9 shown in Table 1, anothermagnifying display device of 4.5×5 mm or 13×15 mm in size may be usedfor the portable image display of the invention.

Instead of the direct-view display device 6 shown in Table 1, anotherdirect-view display device of 30×20 mm or 30×60 mm in size may be usedfor the portable image display of the invention.

The portable image display of the invention may additionally comprise animage data storage for viewing stored image data through the viewingunit. The stored image data may be transmitted and received via acommunication function.

Especially to reduce the size of the viewing unit 2 likely to becomelarge, the storage should be built in the body 1.

As shown in FIG. 4, when viewing image data, it is difficult tomanipulate a set of push buttons 7 because the viewing unit 2 must be aclose to the eye as possible. It is then preferable to use the operatingstick 8. By using the operating stick 8 mounted on the side of theportable image display, operation can be carried out while viewingimages through the viewing optical system.

FIG. 4 shows that the portable image display is held with the left hand.However, it is preferable to add a similar operating stick (not shown)on the opposite side of the body so that operation can be carried outeven when the portable image display is held with the right hand. It isacceptable to attach one detachable operating stick to each side of thebody.

Referring here to the liquid crystal display device 9 in the viewingunit of the invention, a backlight is used as an illumination means whentransmission liquid crystals are used therefor. Thus, when thetransmission liquid crystals are used, it is required to use anillumination optical system therewith. It is then preferable toilluminate the liquid crystal display device 9 using a wedge prism, apowered prism or a diffractive element. FIG. 5 shows an example ofillumination using a wedge prism, wherein 30 stands for a wedge prismand 31 a light source. A light beam emanating from the light source 31is shaped through a beam shaping element 33 and then reflected at theslant surface 32 of the wedge prism 30, so that the liquid crystaldisplay unit 9 can be illuminated. The beam shaping element 33 is madeup of a refracting lens or diffractive optical element.

EXAMPLE 2

Example 2 is constructed as shown in the perspective view of FIG. 6,wherein 1 indicates a portable image display body, 2 a a viewing unitbody, 2 b a reflecting surface of the viewing unit, 3 a speaker, 4 amicrophone, 5 an antenna, 6 a liquid crystal display unit, 7 a set ofpush buttons, 8 an operating stick, and 21 a signal light for indicatingthe end of data reception. As shown in FIG. 7, the viewing unit body 2 acomprises an LCD or other image display device and a prism member forviewing an image displayed on the image display device. The reflectingsurface 2 b of the viewing unit is made up of one reflecting member.When not used as shown by a dotted line 11 in FIG. 7, the reflectingsurface 2 b of the viewing unit can be folded down on the body 1, sothat a compact portable image display can be achieved.

The viewing unit constructed in such a way that it can be folded on thebody 1, does not only achieve compactness but also ensures that when thebody 2 a and reflecting surface 2 b are not used, any possible damage toand contamination of the reflecting surface 2 b can be prevented. Thisis because when folded down on the body 1, the reflecting surface 2 b ispositioned in proximity to the body 1 and so is concealed from theoutside.

This example comprises a magnifying display device and a direct-viewdisplay device 8 having the same specifications as in Table 1 in Example1.

As shown in FIG. 8, the viewing unit comprises a prism member 10 havingan entrance surface 12 for entering a light beam emanating from an imagedisplay device 9 into the prism, reflecting surfaces 13, 14 and 15 forreflecting the light beam in the prism and an exit surface 16 throughwhich the light beam leaves. The reflecting surface 14 has a curvedsurface shape for imparting power to the light beam. Preferably in thisexample, the curved surface shape should be defined by a rotationallyasymmetric surface shape capable of making satisfactory correction forvarious decentration aberrations of the prism and making the prismcompact. After leaving the exit surface 16, the light beam is reflectedat the reflecting surface 17 of the reflecting surface 2 b of theviewing unit to form an exit pupil E. The light beam also forms aprimary image halfway between the exit surface 16 and the reflectingsurface 17. These are combined together to make the prism member 10compact.

The reflecting surface 17 has a curved surface shape for imparting powerto the light beam. Preferably in this example, the curved surface shapeshould be defined by a rotationally asymmetric surface shape capable ofmaking satisfactory correction for various decentration aberrations ofthe prism and making the prism compact.

The portable image display according to this example of the inventionmay additionally comprise an image data storage for viewing stored imagedata through the viewing unit. The stored image data may be transmittedand received via a communication function.

Especially to reduce the size of the viewing unit likely to becomelarge, the storage should be built in the body 1.

As in Example 1, when viewing image data, it is difficult to manipulatea set of push buttons 7 because the viewing unit 2 must be a close tothe eye as possible. It is then preferable to use the operating stick 8.By using the operating stick 8 mounted on the side of the portable imagedisplay, operation Can be carried out while viewing images through theviewing optical system.

As in Example 1, it is preferable to add a similar operating stick (notshown) on the opposite side of the body so that operation can be carriedout even when the portable image display is held with either one of theright and left hands. It is acceptable to attach one detachableoperating stick to each side of the body.

In this example, too, the liquid crystals in the viewing unit may beilluminated as in Example 1.

EXAMPLE 3

Example 3 is constructed as shown in the perspective view of FIG. 9. Inthis example, an image pickup optical system 41 is added to the portableimage display of Example 1. The image pickup optical system 41 comprisesan pickup lens having a generally positive refracting power and a CCD orother image pickup device, so that any desired image can be phototaken.The phototaken image can be viewed through the liquid crystal displaydevice 6, and the viewing unit 2 as well. Using data communicationmeans, the phototaken image data may be transmitted to an otherreceiver.

FIG. 10 is illustrative of a modification to Example 2, wherein an imagepickup optical system 41 is added to the portable image display ofExample 2.

Herein, the image pickup optical system 41 is positioned at the uppersite of the portable image display. However, it is appreciated that theimage pickup optical system 41 may be disposed at any desired site ofthe portable image display. It is acceptable to mount the image pickupoptical system 41 on the image display body in a detachable manner.

EXAMPLE 4

Example 4 is constructed as shown in the perspective view of FIG. 11,wherein a pop-up speaker 42 is mounted on the portable image displaybody 1 of Example 1. When the size of the portable image display of theinvention is too much reduced, the distance between the viewing unit 2and the speaker becomes too short or while the eye is brought nearer tothe viewing unit 2, the speaker is too far away from the ear to catchsounds from the speaker. This inaudible problem can be solved byproviding such a pop-up speaker 42 on the body 1 as shown in FIG. 11.

This example may be applied to the portable image display of Example 2.

EXAMPLE 5

Example 5 is constructed as shown in the perspective view of FIG. 12,wherein a pop-up microphone,43 is mounted on the portable image displaybody 1 of Example 1. When the size of the portable image display of theinvention is too much reduced, the distance between the viewing unit 2and the microphone is too short or while the eye is brought nearer tothe viewing unit, the distance between the microphone and the mouth istoo long to achieve sufficient transmission of sounds to the microphone.This problem can be solved by providing such a pop-up microphone 43 onthe body 1, as shown FIG. 12.

This example may be applied to the portable image display of Example 2.

EXAMPLE 6

Example 6 is directed to prism members 10 used for the viewing opticalsystem and constructed as shown in FIGS. 13 to 20. More specifically,this example is directed to further embodiments of the viewing opticalsystem of Example 1. In these drawings, reference numeral 10 indicates aprism member, 9 stands for a liquid crystal or other image displaydevice, and E represents an exit pupil position. These prism members maybe used for the viewing optical system of the invention, as brieflyexplained below.

Referring to FIG. 13, the prism member 10 comprises a first surface 12,a second surface 13 and a third surface 14. A light beam emanating fromthe image display device 9 enters the prism member 10 upon refraction atthe first surface 12, and reaches the second surface 13 whereat thelight beam is internally reflected. Then, the reflection light entersthe third surface 14 whereat it is refracted, leaving the exit pupil Ein the form of a substantially infinite light beam.

Referring to FIG. 14, the prism member 10 comprises a first surface 12,a second surface 13, a third surface 14 and a fourth surface 15. A lightbeam emanating from the image display device 9 enters the prism member10 upon refraction at the first surface 12, and reaches the secondsurface 13 whereat it is internally reflected. Then, the reflectionlight arrives at the third surface 14 whereat it is internallyreflected, and enters the fourth surface 15 whereat the reflection lightis refracted, leaving the exit pupil E in the form of a substantiallyinfinite light beam.

Referring to FIG. 15, the prism member 10 comprises a first surface 12,a second surface 13 and a third surface 14. A light beam emanating fromthe image display device 9 enters the prism member 10 upon refraction atthe first surface 12, and reaches the second surface 13 whereat therefraction light is totally reflected. The reflection light enters thethird surface 14 whereas it is internally reflected, and goes back tothe first surface 12 whereat the reflection light is now totallyreflected. The reflection light goes back to the second surface 13whereas it is now refracted, leaving through the exit pupil E in theform of a substantially infinite light beams.

Referring to FIG. 16, the prism member 10 comprises a first surface 12,a second surface 13, a fourth surface 14 and a fourth surface 15. Alight beam emitted from the image display device 9 enters the prismmember 10 upon refraction at the first surface 12, and reaches thesecond surface 13 for internal reflection thereat. The reflection lightgoes back to the first surface 12 whereat it is totally reflected, andthe reflection light enters the third surface 14 for internal reflectionthereat. The reflection light enters the fourth surface 15 whereat it isrefracted, leaving through the exit pupil E in the form of asubstantially infinite light beam.

Referring to FIG. 17, the prism member 10 comprises a first surface 12,a second surface 13, a third surface 14 and a fourth surface 15. A lightbeam emitted from the image display device 9 enters the prism member 10upon refraction at the first surface 12, and arrives at the secondsurface 13 for internal reflection thereat. The reflection light entersthe third surface 14 whereat it is internally reflected. The reflectionlight goes back to the second surface 13 for internal reflectionthereat, and enters the fourth surface 15 for refraction thereat,leaving through the exit pupil E in the form of a substantially infinitelight beam.

Referring to FIG. 18, the prism member 10 comprises a first surface 12,a second surface 13, a third surface 14 and a fourth surface 15. A lightbeam emanating from the image display device 9 enters the prism member10 upon refraction at the first surface 12, and arrives at the secondsurface 13 for internal reflection thereat. The reflection light goesback to the first surface 12 for total reflection thereat, and the totalreflection light enters the third surface 14 whereat it is internallyreflected. Then, the reflection light goes back to the first surface 12for total reflection thereat. Finally, the total reflection light entersthe fourth surface 15 for refraction thereat, leaving through the exitpupil E in the form of a substantially infinite light beam.

Referring to FIG. 19, the prism member 10 comprises a first surface 12,a second surface 13 and a third surface 14. A light beam coming from theimage display device 9 enters the prism member upon refraction at thefirst surface 12, and reaches the second surface 13 for internalreflection thereat. The internal reflection light goes back to the firstsurface 12 for total reflection thereat, and arrives at the secondsurface 13 whereat it is totally reflected. Finally, the totalreflection light again goes back to the second surface 13 for refractionthereat, leaving through the exit pupil E in the form of a substantiallyinfinite light beam.

Referring to FIG. 20, the prism member 10 comprises a first surface 12,a second surface 13 and a third surface 14. A light beam emitted fromthe image display device 9 enters the prism member 10 upon refraction atthe first surface 12, and reaches the second surface 13 for totalreflection thereat. The total reflection light goes back to the firstsurface 12 for total reflection thereat, and again reaches the secondsurface 13 for total reflection thereat. The total reflection light goesback to the first surface 12, and again arrives at the second surfacefor total reflection (third time) thereat. The total reflection lightgoes back to the first surface 13 for total reflection (third time).Finally, the total reflection light enters the third surface 14 forinternal reflection thereat, and goes back to the first surface 12whereat it is now refracted, leaving through the exit pupil E in theform of a substantially infinite light beam.

EXAMPLE 7

Example 7 is directed to further embodiments of the viewing opticalsystem of Example 2, as constructed in FIGS. 21 to 25. In thesedrawings, reference numeral 10 indicates a prism member, 17 shows areflecting surface, 9 stands for a liquid crystal or other image displaydevice, and E represents an exit pupil position. The prism member 10 andreflecting surface 17 may be used for the viewing optical system of theinvention, as briefly explained below.

Referring each of FIGS. 21 and 24, the prism member 10 comprises a firstsurface 12, a second surface 13, a third surface 14 and a fourth surface15. A light beam emitted from the image display device 9 enters theprism member 10 upon refraction at the first surface 12. Then, therefraction light reaches the second surface 13 for internal reflection,and arrives at the second surface 14 for internal reflection thereat.Then, the internal reflection light enters the fourth surface 15 forrefraction thereat, leaving the prism member 10 to form an intermediateimage on a primary image-formation plane I. Thereafter, the light isreflected at the reflecting surface 17, leaving through the exit pupil Ein the form of a substantially infinite light beam.

Referring to each of FIGS. 22 and 23, the prism member 10 comprises afirst surface 12, a second surface 13 and a third surface 14. A lightbeam emanating from the image display device 9 enters the prism member10 upon refraction at the first surface 12. Then, the refraction lightreaches the second surface for internal reflection thereat, and goesback to the first surface 12 whereat it is now totally reflected. Then,the total reflection light enters the third surface 14 for refractionthereat, leaving the prism member 10 to form an intermediate image on aprimary image-formation plane I. Thereafter, the light is reflected atthe reflecting surface 17, leaving through the exit pupil E in the formof a substantially infinite light beam.

Referring to FIG. 25, the prism member 10 comprises a first surface 12,a second surface 13, a third surface 14, a fourth surface 15 and a fifthsurface 16. A light beam emitted from the image display device 9 entersthe prism member 10 upon refraction at the first surface 12. Then, therefraction light reaches to the second surface 13 for internalreflection thereat, and arrives at the third surface 14 for internalreflection thereat. Then, the internal reflection light reaches thefourth surface 15 for internal reflection thereat, and enters the fifthsurface 16 for refraction thereat, leaving the prism member 10 to forman intermediate image on a primary image-formation plane I. Thereafter,the light is reflected at the reflecting surface 17, leaving through theexit pupil E in the form of a substantially infinite light beam.

While the portable image display of the present invention has beendescribed with reference to some preferred embodiments, it isappreciated that the present invention is not necessarily limitedthereto; various modifications may be added thereto.

As can be seen from the foregoing explanations, the present inventioncan provide a portable image display wherein the viewing unit thereofcan be made so compact that it can me mounted on portable telephones orinformation terminals.

What is claimed is:
 1. A portable image display having data communication function, comprising: a speaker portion for generating sound, a microphone portion for picking up sound, an image display device, and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refractive power, wherein: said portable image display has a body and a frame member, said frame member is independent of said body and is receivable in said body, said viewing optical system is constructed of at least one prism member comprising an entrance surface through which a light beam emanating from said image display device is entered into a prism, at least one reflecting surface at which said light beam is reflected within the prism and an exit surface through which said light beam leaves the prism, and said at least one reflecting surface has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.
 2. A portable image display having data communication function, comprising: an image display device, and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, wherein: said viewing optical system comprises a prism and a reflecting element having a reflecting surface, said prism being a separate optical element from said reflecting element, said image display device and said prism are received in a body of said portable image display, said reflecting element is held by a frame member which is independent of said body, and said frame member is receivable in said body.
 3. A portable image display having data communication function, comprising: a speaker portion for generating sound, a microphone portion for picking up sound, an image display device, a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, and an image pickup device and an image pickup optical system for forming an image on the image pickup device, wherein: said image pickup device is adapted to generate an electrical signal corresponding to said image formed thereon by said image pickup optical system, said portable image display has a body and a frame member, said frame member is independent of said body and is receivable in said body, and said viewing optical system is constructed of at least one prism member.
 4. The portable image display according to claim 3, wherein: said viewing optical system comprises at least one prism member comprising an entrance surface through which a light beam emanating from said image device is entered into a prism, at least one reflecting surface at which said light beam is reflected within the prism and an exit surface through which said light beam leaves the prism, and said at least one reflecting surface has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.
 5. The portable image display according to claim 1 or 2, which further comprises a data storage device.
 6. The portable image display according to claim 5, wherein said storage device is built in the body thereof.
 7. The portable image display according to claim 1 or 2, which further comprises a light source for illuminating said image display device.
 8. The portable image display according to claim 1 or 2, wherein when an image on said image display device is viewed, said image is turned on the basis of whether the body of said portable image display is held by the right hand or the left hand.
 9. The portable image display according to claim 1, wherein said microphone portion for picking up sounds extends from the body of said portable image display.
 10. The portable image display according to claim 1, wherein said speaker portion for generating sound extends from the body of said image display.
 11. The portable image display according to claim 1, wherein said viewing optical system is mounted in said frame member.
 12. The portable image display according to claim 1 or 2, wherein when said viewing optical system is received in said body, a surface thereof through which a light beam emanating from said image display device leaves is concealed from the outside.
 13. The portable image display according to claim 2, wherein the reflecting surface of said reflecting portion has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction of decentration aberrations.
 14. A portable image display having data communication function, comprising: an image display device, and a viewing optical system for forming an exit pupil to view an image displayed on the image display device and having a generally positive refracting power, wherein: said viewing optical system comprises a prism portion and a reflecting portion having a reflecting surface, said image display device and said prism are received in a body of said portable image display, said reflecting portion is held by a frame member which is independent of said body, said frame member is receivable in said body said viewing optical system comprises at least one prism member comprising an entrance surface through which a light beam emanating from said image device is entered into a prism, at least one reflecting surface at which said light beam is reflected within the prism and an exit surface through which said light beam leaves the prism, and said at least one reflecting surface has a curved surface shape for imparting power to a light beam, said curved surface shape being defined by a rotationally asymmetric surface shape capable of making correction for decentration aberrations.
 15. A portable image display according to claim 2, wherein the reflecting surface of said reflecting element reflects at least the light beam from the image display device. 